Project description:The epithelial-to-mesenchymal transition (EMT) and migration of cranial neural crest cells are critical processes that occur in the early embryo that permit proper craniofacial patterning. Disruptions in these processes not only impair development but also lead to various diseases, underscoring the need for their detailed understanding at the molecular level. The chick embryo has served historically as an excellent model for human embryonic development. While chick cranial neural crest cell EMT and migration have been characterized at the transcript level, studies at the protein level—to allow direct measurement of the active players—have not been undertaken to date. In this study, we applied mass spectrometry (MS)-based proteomics to establish a deep proteomics profile of the midbrain region during early embryonic development. We developed a proteomics method combining optimal lysis conditions and offline fractionation with nanoflow liquid chromatography coupled to high-resolution MS to analyze the tissue from this region, which identified >5,900 proteins involved in key pathways related to neural crest cell EMT and migration such as signaling, proteolysis/extracellular matrix (ECM), and transcriptional regulation. This study offers valuable insight into important developmental processes occurring in the midbrain region and demonstrates the utility of proteomics for characterization of various tissues during chick embryogenesis.
Project description:A systematic survey of the transcriptional status of individual segments of the developing chick hindbrain (r1-5) and the adjacent region of the embryonic midbrain (m) during the HH11 stage of chick development Affymetrix Chicken GeneChip Expression Study Paralell comparison of defined regions of the neural tube during early chick development
Project description:A systematic survey of the transcriptional status of individual segments of the developing chick hindbrain (r1-5) and the adjacent region of the embryonic midbrain (m) during the HH11 stage of chick development Affymetrix Chicken GeneChip Expression Study
Project description:We characterized the proteome of the auditory brainstem of a chick embryo on embryonic day 13, when apoptosis occurs in auditory nuclei. We identified caspase substrates by searching the peptidome for peptides C-terminal to caspase-typical cleavage sites.
Project description:The inner ear develops from a patch of thickened cranial ectoderm adjacent to the hindbrain called the otic placode. Studies in a number of vertebrate species suggest that the initial steps in induction of the otic placode are regulated by members of the Fibroblast Growth Factor (FGF) family, and that inhibition of FGF signaling can prevent otic placode formation. To better understand the genetic pathways activated by FGF signaling during otic placode induction, we performed microarray experiments to estimate the proportion of chicken otic placode genes that can be up-regulated by the FGF pathway in a simple culture model of otic placode induction. Surprisingly, we find that FGF is only sufficient to induce about 15% of chick otic placode-specific genes in our experimental system. However, pharmacological blockade of the FGF pathway in cultured chick embryos showed that although FGF signaling was not sufficient to induce the majority of otic placode-specific genes, it was still necessary for their expression in vivo. These inhibitor experiments further suggest that the early steps in otic placode induction regulated by FGF signaling occur through the MAP kinase pathway. Although our work suggests that FGF signaling is necessary for otic placode induction, it demonstrates that other unidentified signaling pathways are required to co-operate with FGF signaling to induce the full otic placode program. 8 samples were analyzed. These contain two replicates of each of the following four catergories: Otic ectoderm, Non-Otic (lateral) ectoderm, Trigeminal Ectoderm cultured - FGF, Trigeminal Ectoderm cultured + FGF
Project description:TWIST1, a basic helix-loop-helix transcription factor is essential for the development of cranial mesoderm and cranial neural crest-derived craniofacial structures. Our previous work showed that, in the absence of TWIST1, some cells within the cranial mesoderm adopt an abnormal epithelial configuration. Here, we show by transcriptome analysis that loss of TWIST1 in the cranial mesoderm is accompanied by a reduction in the expression of genes that are associated with cell-extracellular matrix interactions and the acquisition of mesenchymal characteristics. By comparing the transcriptional profiles of cranial mesoderm-specific Twist1 loss-of-function mutant and control mouse embryos, we identified a set of genes that are both TWIST1-dependent and predominantly expressed in the mesoderm. By ChIP-seq in a cell line model of a TWIST1-dependent mesenchymal state, we identified, among the downstream genes, three direct transcriptional targets of TWIST1: Ddr2, Pcolce and Tgfbi. Our findings show that the mesenchymal properties of the cranial mesoderm is likely to be regulated by a network of TWIST1 targets genes that influence the extracellular matrix and cell-matrix interactions, and collectively they are required for the morphogenesis of the craniofacial structures. For microarray analysis of CM-CKO embryos, embryo heads of four genotypes were collected at E8.5 (5-7 somites) and E9.5 (18- 20 somites): CM-CKO (Twist1flox/del; Mesp1Cre/+), CM-Het (Twist1flox/wt; Mesp1Cre/+), Het (Twist1flox/del; Mesp1+/+) and Control (Twist1flox/wt; Mesp1+/+). Sample sizes for E8.5 embryos were as follows: Control, n=4 CM-CKO, n=4; Het, n=3; CM-Hets, n=3).
Project description:Hypoxia episodes and areas in tumours have been associated with metastatic dissemination and poor prognosis. Given the link between tumour tissue oxygen levels and cellular metabolic activity, we hypothesised that the metabolic profile between metastatic and non-metastatic tumours would reveal potential new biomarkers and signalling cues. We have used a previously established chick embryo model for neuroblastoma growth and metastasis, where the metastatic phenotype can be controlled by neuroblastoma cell hypoxic preconditioning (3 days at 1% O2). We measured, with fibre-optic oxygen sensors, the effects of the hypoxic preconditioning on the tumour oxygenation, within tumours formed by SK-N-AS cells on the chorioallantoic membrane (CAM) of chick embryos. We found that the difference between the metastatic and non-metastatic intratumoural oxygen levels was small (0.35% O2), with a mean below 1.5% O2 for most tumours. The metabolomic profiling, using NMR spectroscopy, of neuroblastoma cells cultured in normoxia or hypoxia for 3 days, and of the tumours formed by these cells showed that the effects of hypoxia in vitro did not compare with in vivo tumours. One notable difference was the high levels of the glycolytic end-products triggered by hypoxia in vitro, but not by hypoxia preconditioning in tumours, likely due to the very high basal levels of these metabolites in tumours compared with cells. In conclusion, we have identified high levels of ketones (3-hydroxybutyrate), lactate and phosphocholine in hypoxic preconditioned tumours, all known to fuel tumour growth, and we herein point to the poor relevance of in vitro metabolomic experiments for cancer research.
Project description:TWIST1, a basic helix-loop-helix transcription factor is essential for the development of cranial mesoderm and cranial neural crest-derived craniofacial structures. Our previous work showed that, in the absence of TWIST1, some cells within the cranial mesoderm adopt an abnormal epithelial configuration. Here, we show by transcriptome analysis that loss of TWIST1 in the cranial mesoderm is accompanied by a reduction in the expression of genes that are associated with cell-extracellular matrix interactions and the acquisition of mesenchymal characteristics. By comparing the transcriptional profiles of cranial mesoderm-specific Twist1 loss-of-function mutant and control mouse embryos, we identified a set of genes that are both TWIST1-dependent and predominantly expressed in the mesoderm. By ChIP-seq in a cell line model of a TWIST1-dependent mesenchymal state, we identified, among the downstream genes, three direct transcriptional targets of TWIST1: Ddr2, Pcolce and Tgfbi. Our findings show that the mesenchymal properties of the cranial mesoderm is likely to be regulated by a network of TWIST1 targets genes that influence the extracellular matrix and cell-matrix interactions, and collectively they are required for the morphogenesis of the craniofacial structures. For microarray analysis of CM-CKO embryos, embryo heads of four genotypes were collected at E8.5 (5-7 somites) and E9.5 (18- 20 somites): CM-CKO (Twist1flox/del; Mesp1Cre/+), CM-Het (Twist1flox/wt; Mesp1Cre/+), Het (Twist1flox/del; Mesp1+/+) and Control (Twist1flox/wt; Mesp1+/+). Sample sizes for E9.5 were as follows: Control, n=3; CM-CKO, n=4; Het, n=4; CM-Het, n=4). RNA was extracted using the RNeasy Micro kit (Qiagen) and samples sent to the Australian Genome Research Foundation for labelling and hybridization.
Project description:During amniote peripheral nervous system development, segmentation ensures the correct patterning of the spinal nerves relative to vertebral column. Along the antero-posterior (rostro-caudal) axis, each somite-derived half-sclerotome has intrinsic molecular properties that govern this segmentation process. Posterior half-sclerotomes express repellent molecules to restrict axon growth and neural crest migration to anterior half-sclerotomes. Here, we report an RNA-sequencing-based molecular characterization of anterior and posterior half-sclerotomes, using the chick embryo as a model organism.